Calculus - Mr Santowski

Calculus - Mr Santowski
Lesson 31 - Limits Calculus - Mr Santowski 9/19/2018 Mr. Santowski - Calculus & IBHL

Mr. Santowski - Calculus & IBHL
Lesson Objectives 1. Define limits 2. Use algebraic, graphic and numeric (AGN) methods to determine if a limit exists 3. Use algebraic, graphic and numeric methods to determine the value of a limit, if it exists 4. Use algebraic, graphic and numeric methods to determine the value of a limit at infinity, if it exists 5. Be able to state and then work with the various laws of limits 6. Apply limits to application/real world problems 9/19/2018 Mr. Santowski - Calculus & IBHL

Fast Five You will get a hand out of the following three slides. You and your table have 5 minutes to answer the limit questions and then defend your answers (if challenged) 9/19/2018 Mr. Santowski - Calculus & IBHL

Fast Five - Limits and Graphs
9/19/2018 Mr. Santowski - Calculus & IBHL

(A) Find function values at the following: (i) f(-10) = (ii) f(-4) = (iii) f(2) = (iv) f(7) = 9/19/2018 Mr. Santowski - Calculus & IBHL

Find the limit of the function f(x) at the following values: (i) the limit of f(x) at x = -10 is (ii) the limit of f(x) at x = -6 is (iii) the limit of f(x) at x = -4 is (iv) the limit of f(x) at x = 0 is (v) the limit of f(x) at x = 2 is (vi) the limit of f(x) at x = 4 is (vii) the limit of f(x) at x = 6 is (i) the limit of f(x) at x = 7 is (i) the limit of f(x) at x = 10 is 9/19/2018 Mr. Santowski - Calculus & IBHL

(A) Introduction to Limits
Let f be a function and let a and L be real numbers. If 1. As x takes on values closer and closer (but not equal) to a on both sides of a, the corresponding values of f(x) get closer and closer (and perhaps equal) to L; and 2. The value of f(x) can be made as close to L as desired by taking values of x close enough to a; Then L is the LIMIT of f(x) as x approaches a Written as limxa f(x) = L 9/19/2018 Mr. Santowski - Calculus & IBHL

We will work with and consider the function behaviour at x = 2 We can express this idea of function behaviour at a point using limit notation as 9/19/2018 Mr. Santowski - Calculus & IBHL

We will explore the limit in a variety of ways: first using a ToV So notice what happens to the function values as x gets closer to 2 from both sides (RS 2.01, 2.02 & LS 1.98, 1.99) So we can predict a limiting function value of 12 9/19/2018 Mr. Santowski - Calculus & IBHL

We will explore the limit in a variety of ways: now using a graph and tracing the function values 9/19/2018 Mr. Santowski - Calculus & IBHL

Now we can use the TI-89 to actually calculate the limit value for us So we have the confirmation of the limiting function value of 12 as we had previously with the table and the graph 9/19/2018 Mr. Santowski - Calculus & IBHL

(B) Determining Values of Limits
Now, how does all the algebra tie into limits? If we try a direct substitution to evaluate the limit value, we get 0/0 which is indeterminate 9/19/2018 Mr. Santowski - Calculus & IBHL

Is there some way that we can use our algebra skills to come to the same answer? Four skills become important initially: (1) factoring & simplifying, (2) rationalizing and (3) common denominators and (4) basic function knowledge 9/19/2018 Mr. Santowski - Calculus & IBHL

Consider the expression Now can we factor a difference of cubes? 9/19/2018 Mr. Santowski - Calculus & IBHL

So then, 9/19/2018 Mr. Santowski - Calculus & IBHL

Determine the following limits. Each solution introduces a different “algebra” trick for simplifying the rational expressions Verify limit on GDC 9/19/2018 Mr. Santowski - Calculus & IBHL

(C) Existence of Limits
Find So we try to use some algebra “tricks” as before, but x2 + 9 doesn’t factor. So we use a ToV, and a graph What is the limit in this case? 9/19/2018 Mr. Santowski - Calculus & IBHL

In this case, both the graph and the table suggest two things: (1) as x3 from the left, g(x) becomes more and more negative (2) as x3 from the right, g(x) becomes more and more positive 9/19/2018 Mr. Santowski - Calculus & IBHL

So we write these ideas as: & Since there is no real number that g(x) approaches, we simply say that this limit does not exist 9/19/2018 Mr. Santowski - Calculus & IBHL

Now here is a graph of a function which is defined as Find limx2f(x) 9/19/2018 Mr. Santowski - Calculus & IBHL

Now find the limit of this function as x approaches 2 where f(x) is defined as i.e. determine limx2f(x) 9/19/2018 Mr. Santowski - Calculus & IBHL

In considering several of our previous examples, we see the idea of one and two sided limits. A one sided limit can be a left handed limit notated as which means we approach x = a from the left (or negative) side We also have right handed limits which are notated as which means we approach x = a from the right (or positive) side 9/19/2018 Mr. Santowski - Calculus & IBHL

We can make use of the left and right handed limits and now define conditions under which we say a function does not have a limiting y value at a given x value ==> by again considering our various examples above, we can see that some of our functions do not have a limiting y value because as we approach the x value from the right and from the left, we do not reach the same limiting y value. Therefore, if then does not exist. 9/19/2018 Mr. Santowski - Calculus & IBHL

(E) Limit Laws The limit of a constant function is the constant The limit of a sum is the sum of the limits The limit of a difference is the difference of the limits The limit of a constant times a function is the constant times the limit of the function The limit of a product is the product of the limits The limit of a quotient is the quotient of the limits (if the limit of the denominator is not 0) The limit of a power is the power of the limit The limit of a root is the root of the limit 9/19/2018 Mr. Santowski - Calculus & IBHL

(E) Limit Laws Here is a summary of some important limits laws: (a) sum/difference rule  lim [f(x) + g(x)] = lim f(x) + lim g(x) (b) product rule  lim [f(x)  g(x)] = lim f(x)  lim g(x) (c) quotient rule lim [f(x)  g(x)] = lim f(x)  lim g(x) (d) constant multiple rule  lim [kf(x)] = k  lim f(x) (e) constant rule  lim (k) = k These limits laws are easy to work with, especially when we have rather straight forward polynomial functions 9/19/2018 Mr. Santowski - Calculus & IBHL

(E) Limit Laws and Graphs
9/19/2018 Mr. Santowski - Calculus & IBHL

(E) Limit Laws and Graphs
From the graph on this or the previous page, determine the following limits: (1) lim x-2 [f(x) + g(x)] (2) lim x-2 [(f(x))2 - g(x)] (3) lim x-2 [f(x) × g(x)] (4) lim x-2 [f(x) ÷ g(x)] (5) lim x1 [f(x) + 5g(x)] (6) lim x1 [ ½f(x) × (g(x))3] (7) lim x2 [f(x) ÷ g(x)] (8) lim x2 [g(x) ÷ f(x)] (9) lim x3 [f(x) ÷ g(x)] 9/19/2018 Mr. Santowski - Calculus & IBHL

(G) Internet Links Limit Properties - from Paul Dawkins at Lamar University Computing Limits - from Paul Dawkins at Lamar University Limits Theorems from Visual Calculus Exercises in Calculating Limits with solutions from UC Davis 9/19/2018 Mr. Santowski - Calculus & IBHL

(G) Internet Links Limits Involving Infinity from Paul Dawkins at Lamar University Limits Involving Infinity from Visual Calculus Limits at Infinity and Infinite Limits from Pheng Kim Ving Limits and Infinity from SOSMath 9/19/2018 Mr. Santowski - Calculus & IBHL

(I) “A” Level Investigation
Research the DELTA-EPSILON definition of a limit Tell me what it is and be able to use it MAX 2 page hand written report (plus graphs plus algebra) + 2 Q quiz 9/19/2018 Mr. Santowski - Calculus & IBHL

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